The invention relates to a bus system for connecting a plurality of data processing units by means of a bus that consists of two signal lines.
Up to now, data processing unit processing systems are mainly coupled together by means of digital bus systems, wherein standardized protocols such as Ethernet (IEEE 802.3) are being used, based upon which network protocols such as TCP/IP or similar are being utilized. Ethernet connections with data transfer rates of 100 Mbit/s are presently widely in use because of the high data transfer rate, the low costs and the sturdiness of the system. A disadvantageous fact is that two separate pairs of wires are required for the data transmission and reception, which doubles the weight of the lines compared to other protocols such as ARINC-429 or MIL-STD-1553 or CAN, which require only one pair of wires. Another substantial disadvantage consists in that only point-to-point connections are possible and that active couplers such as hubs or switches are required to build up a network with multiple participants. If the Ethernet is to be operated in a deterministic manner with guaranteed bandwidths and/or guaranteed maximum delays, this requires complex protocols for controlling the media access (so-called MAC protocols). These are based either on the TDMA principle (time division multiple access) or require complex, priority-ontrolled buffer and transmission rate restriction concepts.